Shield for boiler-furnaces



(No Model.)

'W'. MADDEN.

SHIELD FOR BOILER FURNACES.

Patented Jan. 18, 1887.

N. PKYERS. PmlwLillwgnphnr. Wishmglom o. c

NrrEn STATES PATENT OFFICE.

\VILLIAM MADDEN, OF SAN FRANCISCO, CALIFORNIA.

SHIELD FOR BOILER-FURNACES.

SPECIFICATION forming part of Letters Patent No. 356,285, dated January 18, 1887.

Application filed May 24, 1886. Serial No. 203,157. (No model.)

tion which is specially useful in connection with boiler furnaces where great heat is brought upon the angles and flanges of certain portions of the boiler.

It consists of a protecting-shield for these portions, by which they are relieved from the effects of excessive heat, and leakage by the constant unequal expansion and contraction is avoided.

Referring to the accompanying drawings for a more complete explanation of my invention, Figure l is a sectional elevation of a boiler, showing the application of my device. Fig. 2 is a perspective view of the device.

In the present case I have shown my invention applied to boilers of that class having large dues in the lower part, with grates upon which the fire is built, bridge-walls at the rear end, and a combustionchainber at the rear of the bridgewall into which the products of combustion pass, return-flues or small tubes through Which the heat and flame are brought, and the uptake and smoke-stack at the'front ot' the boiler. These boilers are usually made short, and where the high pressure of steam is carried must be made correspondingly thick and strong.

At the point a the flanges of the inner head or the flue sheet are turned and riveted to the shell of the furnace, making a 1ap-joint and considerable thickness, and the exterior of this angle is exposed to the most intense heat from the fire while the interior is in contact with the water of the boiler. The thickness of the metal is such that very unequal expan sion takes place at this point, and the result is a strain which causes leakage, so that it is almost impossible to keep the joint tight, and the boilers need constant overhauling and repair on this account. In order to protect this portion from the direct action of the flame and heat of the fires, I form an arch of fireclay-or brick, as shown at b, which extends a short distance each side of the'' joint and prevents actual contact of the flame with it. This arch may be either built of fire-brick or fire-clay. In the present case I have shown a semicircular iron arch or hoop having feet or flanges at the bottom, supported upon the bridge-wall at each end, and it is provided with projecting lugs or ridges, 0, within which the body of fire-clay or the fire-brick may be held and prevented from falling outof place. This prevents the direct action of the heat upon the angle and prevents it from great and unequal expansion, which would otherwise take place, and prevents the strain and consequent leakage at this point.

Having thus described my invention, what I claim as new,and desire to secure by Letters Patent, is

I. Aprotectingshield for boilers, comprising a flanged semicircular iron arch or hoop supported upon the bridge-wall, and provided with lugs or ridges for securing fire-clay or firebrick, substantially as herein described.

2. In a boiler-furnace, aprotecting shield or arch formed of fire-clay, fire-brick, or other fire-resisting material, said arch or circle ex- WILLIAM MADDEN.

\Vitnesses:

S. H. NoURsn, H. C. LEE. 

